Stages of breast cancer

Staging describes or classifies a cancer based on how much cancer there is in the body and where it is when first diagnosed. This is often called the extent of cancer. Information from tests is used to find out the size of the tumour, what part of the breast has cancer, whether the cancer has spread from where it first started and where the cancer has spread. Your healthcare team uses the stage to plan treatment and estimate the outcome (your prognosis).

The most common staging system for breast cancer is the TNM system. For breast cancer there are 5 stages – stage 0 followed by stages 1 to 4. Often the stages 1 to 4 are written as the Roman numerals I, II, III and IV. Generally, the higher the stage number, the more the cancer has spread. Talk to your doctor if you have questions about staging.

When describing the stage of breast cancer, sometimes doctors group them as follows:

In situ breast cancer – The cancer cells are only in the duct or lobule where they started and have not grown into nearby breast tissue (non-invasive). It is stage 0.

Early stage breast cancer – The tumour is smaller than 5 cm and the cancer has not spread to more than 3 lymph nodes. It includes stages 1A, 1B and 2A.

Locally advanced breast cancer – The tumour is larger than 5 cm. The cancer may have spread to the skin, the muscles of the chest wall or more than 3 lymph nodes. It includes stages 2B, 3A, 3B and 3C. Inflammatory breast cancer is also considered locally advanced breast cancer.

Metastatic breast cancer – The cancer has spread to other parts of the body. It is stage 4.

There are several groups of lymph nodes around each breast. The stage often depends on which lymph nodes the cancer has spread to.

Stage 0 (carcinoma in situ)

One of the following applies:

There are cancer cells only in the lining of a breast duct. This is called ductal carcinoma in situ (DCIS).

There is a buildup of abnormal cells in the breast lobules. This is called lobular carcinoma in situ (LCIS).

There is Paget disease of the breast without any invasive carcinoma, DCIS or LCIS.

Stage 1A

The tumour is 2 cm or smaller.

Stage 1B

The tumour is 2 cm or smaller, or no tumour can be seen in the breast. A small number of cancer cells are found in the lymph nodes (micrometastases). Each lymph node with cancer cells in it is no larger than 2 mm.

Stage 2A

The tumour is 2 cm or smaller, or no tumour can be seen in the breast. Cancer cells are found in 1 to 3 lymph nodes under the arm (axillary lymph nodes), in lymph nodes inside the chest around the breastbone (internal mammary lymph nodes) or in both areas.

Or the tumour is larger than 2 cm but not more than 5 cm.

Stage 2B

The tumour is larger than 2 cm but not more than 5 cm. The cancer has also spread to 1 to 3 axillary lymph nodes, internal mammary lymph nodes or both areas.

Or the tumour is larger than 5 cm.

Stage 3A

The tumour is 5 cm or smaller, or no tumour can be seen in the breast. Cancer cells are found in 4 to 9 axillary lymph nodes, or in internal mammary lymph nodes but not in axillary lymph nodes.

Or the tumour is larger than 5 cm. The cancer has also spread to 1 to 9 axillary lymph nodes or to internal mammary lymph nodes. Or it may have spread to 1 to 3 axillary lymph nodes and internal mammary lymph nodes.

Stage 3B

The tumour has grown into the muscles of the chest wall or the skin or both. The cancer may have also spread to 1 to 9 axillary lymph nodes or to internal mammary lymph nodes. Or it may have spread to 1 to 3 axillary lymph nodes and internal mammary lymph nodes.

Stage 3C

The cancer has spread to 10 or more axillary lymph nodes or to lymph nodes below the collarbone (infraclavicular lymph nodes).

The cancer has spread to more than 3 axillary lymph nodes and internal mammary lymph nodes.

The cancer has spread to lymph nodes above the collarbone (supraclavicular lymph nodes).

Stage 4

The cancer has spread to other parts of the body (called distant metastasis), such as to the bone, liver, lungs or brain. This is also called metastatic breast cancer.

Recurrent breast cancer

Recurrent breast cancer means that the cancer has come back after it has been treated. If it comes back in the same place that the cancer first started, it’s called local recurrence. If it comes back in tissues or lymph nodes close to where it first started, it’s called regional recurrence. It can also recur in another part of the body. This is called distant metastasis or distant recurrence.